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Security in depth · Unit 22 · Lesson 10 of 44
Scheduled work inherits a trust chain
Separate a timer firing from a successful job and a verified output.
Helpful before thisLinux privilege escalation
After this lesson you can
- Interpret trigger, service identity, dependency, and output records without assuming success.
One idea. One situation. One reasoned decision.
How it works
A systemd timer activates a unit, commonly a service. The service’s execution configuration determines its runtime identity and environment. Protecting the timer does not by itself protect the program, configuration, input permissions, or output destination.
An activation record also does not prove a successful result. Review the trigger, the actual execution, and the intended business output as separate evidence.
Read the supplied record
T1 concerns a fictional nightly summary. Nina requires a fresh approved report before 06:00.
| Evidence | Supplied observation |
|---|---|
| Timer | Activated report service at 02:00 |
| Acting service identity | export-worker |
| Schedule and program updates | Restricted to release maintainers |
| Job result | Failed at 02:01; input unavailable |
| Output record | Last completed report is yesterday’s |
Assume these records refer to the same run and that no later successful run or alternative delivery is supplied. The protected trigger worked, but freshness is not demonstrated. The failure does not prove whether the input was missing, inaccessible, or temporarily unavailable; the packet has not established that cause.
Ask the service owner to assign the dependency investigation and approve a recovery plan that preserves the intended identity and permissions. Broadening access merely to make an error disappear would need independent justification.
Acceptance should connect a completed run to the correct reporting period, approved fields, and intended destination. Retain the failure and recovery evidence together. A previous valid report can be useful context, but presenting it as today’s result would conceal the unresolved delivery gap.
The key distinction: A successful trigger is evidence of activation, not completion or correctness.
Check yourself
No timer. No penalties. Read the explanation and try again whenever you like.
This lesson’s questions have changed. Your reading progress is saved; review the updated questions.
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What should the reviewer conclude from T1?
Show the answer
Correct answer: The timer activated the service, but the approved fresh-output requirement is not verified. The failure record and yesterday’s output contradict treating activation as evidence of successful delivery.
Try it
- WriteCreate a four-row evidence note for T1: trigger, execution identity, dependency failure, and output freshness. State whether delivery is verified and what owner-approved evidence is still needed.